Common colds appear to be caused by a number of viruses or at least a number of strains of viruses which explains the remarkably transient immunity to colds and the fact that reinfection can take place within as little as three weeks of an apparent recovery. No ailment is quite so universal as the common cold and, indeed, it is probably the commonest of all infectious diseases.
An institution that has played a major role in the investigation of the cold is The Medical Research Council, Common Cold Unit, Salisbury, England. Investigations and tests at MRC during the past forty years have proven that the common cold is caused by rhinoviruses that enter the body mainly by the nostrils, and are usually transmitted by an infected person, sometimes by a simple handshake, that will often carry the virus to the facial cavities and there contact the mucus membranes. A good sneeze from an infected person in a public place will disseminate a vast number of droplets among those present, some of whom will quite likely acquire an upper respiratory tract infection.
The infection produced by the rhinovirus is an acute one, and like other acute infections, it may clear up in the course of only a few days. Frequently, however, secondary invaders follow upon the primary infection, and these convert an otherwise acute injection into a chronic disease which may drag on for several unpleasant weeks. These secondary invaders attack first the nose and throat and may later spread to the larynx, trachea, bronchi and up into the sinuses which open into the nose. For the first day or so, the mucus membrane lining of the nose and throat is swollen, red and dry, giving the all too well known symptoms of feeling "stuffed-up". Soon the nose secretes a watery fluid which runs from the nose continually. Secondary invaders change the nature of the inflammation from a watery secretion to one that is more purulent which may continue to be discharged for several weeks.
Folk medicine through the years has suggested the uses of endless numbers of remedies, including pine-needle, honeysuckle, chrysanthemum and licorice teas. Some people believe in sweating the cold out, or taking a hot alcoholic beverage and aspirin before going to bed at night are useful, although there is a theory that aspirin aggravates the common cold.
More recent treatments for the common cold include the use of topically-applied sympathomimetic drugs which exert a vasoconstrictor action directly on the mucus membrane to which they are applied. An example of such a drug is epinephrine, although other more recently developed longer-acting drugs are preferred. All of these have the disadvantage that their use may be followed by "after congestion" and that prolonged use over a period of time often results in chronic rhinitis. Ephedrine and pseudoephedrine, also sympathomimetic drugs, have been given orally as nasal decongestants either by themselves or in combination with a variety of other agents including antihistamines, analgesics, caffeine, antitussives or antimuscarinic drugs. Of this last-mentioned category, atropine and belladonna alkaloids are the most commonly used to reduce secretions in both the upper and lower respiratory tract, including reducing the volume of bronchial secretion. It is recognized that this therapy does not affect the natural course of the condition for which the drugs are administered; see Goodman and Gilman. The Pharmacological Basis of Therapeutics (1975), at page 529. All of these drug substances discussed above are used to treat the symptoms of the infection and, to make the patient more comfortable while the infection runs its normal course of several days to over a week.
Despite extensive discussions in the literature of folk medicine and current therapeutics, little has been written about the fact that some individuals' nasal acid system destroys invading rhinoviruses. These germ-destroying properties of such acidic conditions are particularly useful in the nasal passages which, under normal conditions, provide secretions that are only slightly on the acid side. It is believed that this acidic-type environment makes the nasal passages and mucus membranes an inhospistable environment for invading rhinoviruses.